The present invention relates generally to electro-optical scanning systems adapted to sense a bar-code pattern for generating data representing digital signals and more particularly, to a low cost scanning apparatus for generating scanning beams used in scanning a bar code pattern.
In present-day merchandising point-of-sale operations, data pertaining to the merchandised item purchased is obtained by reading data encoded indicia such as a bar code printed on the merchandised item. In order to standardize the bar codes used in various point-of-sale readout systems, the grocery industry has adopted a Universal Product Code (UPC) which is in the form of a bar code. Various reader systems have been constructed to read this bar code including hand-held wands which are moved across the bar code and stationary optical reader systems normally located within the checkout counter in which the portion of the merchandise item containing the bar code is moved across a window, constituting the scanning area of the counter, which movement is a part of the check-out process just prior to loading the item in a bag or the like.
The stationary scanning systems presently available utilize a rotating mirror for generating a scan pattern used in reading the bar code. Examples of this type of scanning system may be found in U.S. Pat. Nos. 3,916,158, 3,995,166 and 4,057,784. Limitations of this type of scanning structure include tight mechanical requirements due to the high speed rotation of the mirror, which requirements limit the operating efficiency of such scanning apparatuses.
In addition, this type of scanning apparatus by necessity is large in size and weight and therefore high in cost. In order to improve the efficiency of the stationary scanning systems, scanning systems have been suggested in which the light beam reflected from one facet of a rotating multifaceted mirror is reflected back to an adjacent facet, thereby following the facet as it rotates to expand the power of the light beam as it scans towards the edge of the document to be scanned. An example of this type of scanning apparatus may be found in U.S. Pat. No. 4,213,157. While the scanning apparatus of the above-cited United States Patent provides the intended scanning operation, the construction is very complex and therefore high in cost. It is therefore an object of this invention to provide an improved low cost scanning apparatus for generating a multi-line scan pattern in a bar code reader. It is a further object of this invention to provide an improved low cost scanning apparatus which generates a plurality of scanning light beams used in forming a scan pattern using a single light source. It is another object of this invention to provide an improved low cost scanning apparatus which generates a complex scan pattern at maximum power throughput and speed.